This website is a fantastic tutorial!
It explains zbuffering, octrees, backface culling, uv normals,
perspective correction, world/camera coorinate systems,
matrices, texture mapping, and so much more!
It touches on almost everything, and provides examples, and/or links to other
sources.
http://gamecode.tripod.com/tut/Check it out! Seriously, its the easiest to grasp one I've found yet.
It just makes the fact that this engine works so well, even more of a wonder;)
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By the way, somehow I am able to make this a sticky. I was under the impression only mods could do this :twisted: